I thought I'd pass along some tips a Medtronic trainer gave me the other day.
Some background, I've had issues with sensors on and off since I started my 530g(got it in May). Basically two main issues, poor performance in the first 24 hours, and sensors not surviving the full 6 days. I've been a good trooper and called the Medtronic helpline each time I had problems so they could document them, and so I could get a replacement sensor(at no charge). I then had the helpline contact my regional clinical manager to see if they could see if I was doing something wrong or if they had suggestions. I then met with my local Medtronics clinical manager who is a RN, CDE, AND a Type 1 that uses the 530g. This was only a week ago so I'll just give you the tips that I know help.
Poor performance in the first 24 hours was driving me insane.
Tip 1: The first calibration needs to be done when your "Cal Factor" is between 3-8. Cal Factor = "Current fingerstick BG divided by the current "Sensor Isig" value. Sensor Isig can be found on the Sensor Status screen. If the "Cal Factor" is higher or lower, you will get bad readings for the next entire day since the the CGM uses the last 4 calibrations as a baseline. This has proven accurate
I use IV3000 as overtape for my Sensor mainly for comfort since I'm pretty physically active.
Tip 2: Each sensor comes with 2 pieces of overtape. Use one normally then cut another in half. Attach the sensor as you were taught to, plug in and secure the transmitter as normal. Then take half of the tape you cut and put it over the front of the sensor to make it more secure. You can then use the second half over the back third of the transmitter or do like me and cut an IV3000 in half and just put it over the back third of the Transmitter. This will keep the middle of the transmitter exposed so that water can drain easily when you shower while still giving you the security of overtaping.
I have been only attaching my sensor to my abdomen, mainly because I'm lean/muscular and didn't think I could attach it elsewhere.
Tip 3: We found a couple of alternative sites on me that might work for you. The inner thigh, I currently have my sensor here, its working like a charm and I can hardly tell it's there. The top of the butt below the beltline but above the part you sit on. I haven't tried this yet but it seems like it would work well.
That's all I have for now, I'll let you know if anything else comes along that might help.